(a) Field of the Invention
The present invention is related to a display overdrive method applicable to picture process for various types of displays, and more particularly to one that applies mapping to change gray scale range and adjust gamma voltage to reduce response time thus to upgrade picture quality.
(b) Description of the Prior Art
In image process technology, unlike the conventional CRT that works by having electron beam to collide against a screen coated with light emitting material, the luminance display of an LCD takes time to drive liquid crystal molecules to react with voltage (response time) due to the LCD is subject to the inherited nature of the liquid crystal molecule, e.g. sticking coefficient, dialectic constant and elasticity coefficient. Generally, the response time is divided into two parts:                (1) Rising response time (Tr): i.e., with the applied voltage, the time raising taken for the luminance of the liquid crystal box of the LCD to change from the level of 10% up to 90%.        (2) Falling response time (Tf), i.e., without the applied voltage, the time falling taken for the luminance of the liquid crystal box to change from the level of 90% down to 10%.        
Image data transmitted to the display is comprised of multiple frames. When the display rate of the picture is greater than 25 frames per second, the fast changed pictures will become continuous picture to human eyes thus to create visual pictures including dynamic film and TV game animation. Usually, the display rate of the movies or animation is greater than 60 frames per second, meaning each frame time is equal to 1/60 sec.=16.67 ms. When the response time of the LCD is greater than that frame time, ghost or twitching trace appears on the picture to seriously affect viewing quality. Efforts to upgrade technology for reducing LCD response time are generally inputted in the directions, respectively, lowering the sticking coefficient, reducing the liquid crystal box spacing, increasing the dialectic coefficient, and increasing the drive voltage. Wherein, other than increasing the drive voltage, all the remaining directions involve coordination from liquid crystal materials and manufacturing process. For the increased drive voltage technology, it may enter from the method to drive the liquid crystal panel to further improve gray scale response rate without significantly changing the construction of the display panel. This technology is referred as Overdrive (OD) technology; wherein, increased voltage is transmitted from a driver IC to the liquid crystal panel to increase the rising voltage of the liquid crystal for it to engage in faster cycle of rising and falling thus to quickly arrive at the luminance desired to be present by the image data with shortened response time.